@article{LethermanSchleicherWood1999,
  author    = {{Simon Letherman, Dierk Schleicher and Reg Wood}},
  title     = {{On the $3X+1$ problem and holomorphic dynamics}},
  journal   = {{Experimental Math.}},
  year      = {{1999}},
  volume    = {{8}},
  number    = {{3}},
  pages     = {{241--251}},
  note      = {{MR 2000g:37049}},
}